Hierarchies of data base languages: An example

摘要

In view of a manufacturer's investments, commercially available data base systems usually offer comparatively general-purpose interfaces. In order to adapt these interfaces to the special problems of a particular user considerable effort in time, money and personnel is required by the user. Therefore, one might ask whether, (a) construction rules may be found which simplify the process of adaptation and (b) new interfaces may be defined which are both more problem-oriented and still economical enough to be standardized. Based on the notion of hierarchy of abstract machines, this paper attempts to present a possible approach to the solution of these questions. In particular, a set-theoretic and a natural-German interface are suggested. These interfaces as well as some implementation aspects will be motivated, defined, and illustrated by means of a system currently in operation at the university of Karlsruhe. The advantages of a set-theoretic approach as well as the problems associated with a natural language interface will be discussed.